How bad is the air in Beijing?It’s downright awful. Beijing’s thick, nasty combination of carbon monoxide, sulfur dioxide, nitrogen dioxide, and assorted particulate matter is 40 times worse than the smog in Los Angeles, the U.S.’s most polluted city. Depending upon the weather, a dense yellowish haze sometimes blankets the entire metropolis. Researchers estimate that up to 400,000 Chinese die prematurely from air pollution annually, with as many as 25,000 deaths in Beijing alone.

Why so much smog?China has never paid much attention to air pollution, and its ferocious economic development has made its bad air much worse. In the seven years since Beijing was awarded the Olympics, which begin Aug. 8, the nation’s industrial output has increased 80 percent. Most of this growth has been fueled by primitive, coal-fired furnaces and boilers, which spit out tons of choking hydrocarbons. There are also about 3.3 million cars on Beijing’s roads—triple the number a decade ago—belching noxious gases. Natural factors are at work, too. Dust storms in nearby deserts throw tons of soil into the air, and because mountains surround Beijing on three sides, pollutants tend to stay trapped there, like soup in a bowl.

What does all this mean for athletes?Trouble, in the form of labored breathing, reduced metabolic efficiency, and general misery. Last September, Adam Craig of the U.S. mountain biking team dropped out of a training race in Beijing, citing the pollution. “My lungs stopped working,” he said. “It started with a routine deep breath on a descent, which produced a sharp pain and a fit of hacking, then progressed rapidly to a state where I was unable to take more than a quarter of a breath.” More recently, four American boxers jogging outside in Beijing developed breathing problems. So they began training by running up and down the corridors of their hotel. Jarrod Shoemaker, a U.S. triathlete, says Beijing air is so dirty that you can taste it. “You can feel the grit in your teeth,” he says. “In 2007 we wore masks when we weren’t racing.”

Is China dealing with the problem?It’s certainly trying. When China won its Olympic bid in 2001, it promised to meet the World Health Organization’s air quality standards, and it has spent $17 billion on that effort. In advance of the Olympics, authorities have shut down or relocated 200 notoriously polluting plants and factories. They have also temporarily closed 1,000 coal mines and 144 gas stations. Beginning July 20, half of the city’s automobiles—about 1.5 million cars—were banned from city streets for the duration of the Games, and all city construction has been halted. “After we fully implement all of the Olympic measures,” said environmental official Zhang Lijun, “it will be no problem for the air quality to meet acceptable standards.”

Has it met those standards?To some extent. Last year Beijing had 246 “blue sky” days of low or moderate pollution, up from only 100 in 1998. The Beijing Olympic Organizing Committee says pollution levels have dropped 13.8 percent since 2001. For most of June, pollution in Beijing averaged 87.75 on a government index of 500—a level that Chinese officials consider safe. But that’s still double the typical levels in most Western cities. A recent study by the London Times concluded that Beijing’s pollution remains up to five times worse than levels deemed safe by the World Health Organization. Although Beijing’s own Environmental Protection Bureau rates the current air quality as “fair,” independent environmental consultant Steven Andrews says air quality in Beijing “was actually worse in 2006 and 2007 than in 2000 and 2001.”

How are athletes reacting?Many are staying clear of the capital for as long as possible. The U.S. track-and-field team is training in the eastern port city of Dalian, and its coaches are advising the athletes to wear dust masks once they get to Beijing. The Canadians will work out in Singapore until a few days before their events; the entire British delegation is holed up in Macau. Australia’s track-and-field team will skip the opening ceremonies, remaining at training camps outside China until it begins competing. Haile Gebrselassie of Ethiopia, the world’s fastest long-distance runner, has announced that while he’ll compete in the 10,000-meter race, he’ll pass on the marathon. “It’s going to be the hardest marathon in history,” said Gebrselassie. “I’d love to go for it, but health is my first priority.”

Will the air affect the Games? It’s anyone’s guess. Officials insist that the vehicle restrictions and industrial shutdowns will cut pollutants by as much as 40 percent. But these restrictions have just begun, so the impact on Beijing’s air has yet to be seen. In any event, the International Olympic Committee will monitor air quality every day and decide if endurance events such as the triathlon may proceed safely. IOC President Jacques Rogge points out that the Games have always had to contend with weather and other external forces. “If the atmospheric conditions are too cold in cross-country, or if it’s too hot for a marathon, we change the dates,” he says. “Yes, it is true that the pollution in Beijing is today a question mark. But we adapt.”

An ecological catastropheAfter the Olympic athletes leave, China’s 1.6 billion people will still have to deal with the country’s tainted air, land, and water. The problem extends well beyond Beijing; 16 of the world’s 20 most polluted cities are in China. The extent of the problem is staggering: China produces a third of the world’s garbage, only 10 percent of which is recycled; an estimated 7 billion tons of trash remain untreated in landfills. More than 70 percent of China’s rivers are contaminated, and half a billion of its people lack access to potable water. Future generations already are being affected: Chinese officials have linked pollution to the country’s 40 percent rise in birth defects since 2001. In recent years, Chinese citizens have gotten fed up with drinking fouled water and breathing visible air. There have been thousands of anti-pollution demonstrations throughout China, some of which have turned into riots. “We’re not dissidents,” said Wen Di, a blogger who protested the opening of a petrochemical factory in Chengdu, Sichuan province, in May. “We’re just people who care about our homeland.”